Water quality index, hydrogeochemical facies and pollution index of groundwater around Middle Benue Trough, Nigeria

Water quality index (WQI), hydrogeochemical facies and pollution index of groundwater (PIG) of Doma, were carried out to determine the groundwater quality for drinking and irrigation purpose since majority of the dwellers within the locality depend on groundwater for their daily needs, and there has been no detailed study around the area on the subject matter. 16 groundwater samples were collected and analyzed from the area for its physical and chemical constituent using appropriate methods. The result shows that the dominant ionic specie in the cations are Na + K, while Cl is the dominant ionic specie for the anions, with a hydrogeochemical trend of Cl+ > Na+ + K+ > Ca+ > Mg+ > SO4 > HCO3− + CO3. The Contamination Factor (CF) revealed that it is only Mg and Sulphate that has values less than 1, other parameters had CF values ranging between low concentrations to very high concentration. The Pollution Load Index results showed that 74.5% of the groundwater samples had no pollution, 6.25% were moderately polluted, 6.25% had heavy pollution, while 12.5% were extremely polluted. WQI indicated that the entire samples were not fit for drinking, irrigation nor industrial purposes. The PIG results showed that 50% had insignificant pollution, 25% had low pollution while 25% had very high pollution. Principal Component Analysis result indicated that in PC1, 69.2% had loadings (TDS, Conductivity, Na, K, Ca, Mg, Pb, Cl, and NO3). For PC 2, 30.8% of the variables had loading (pH, Fe, HCO3). Sodium Absorption Ratio results showed that 87.5% of the water was excellent and 12.5% was good for irrigation. Bicarbonate Hazard results indicated a safe, marginal and unsuitable as 31.25%, 25% and 43.75%, respectively. Magnesium Hazard results showed that 56.25% of the samples were safe while 43.75% were not. Percentage sodium results revealed that 6.25%, 25%, 50% and 18.75% of the samples were excellent, permissible, doubtful, and unsuitable, respectively. Kelly’s Ratio results indicated that 43.75% were suitable while 56.25 were unsuitable. Total Hardness results showed that 81.25% of the water samples were soft, 12.50%, moderately hard and 6.25%, very hard. TDS result results showed that 93.75% were suitable while 6.25% were moderately suitable. EC results showed that 75% of the samples were excellent, 18.75% (good) and 6.25% (permissible). The Wilcox diagram revealed low-to-medium salinity with only one sample having high salinity values. Based on these results, the water in